双馈风机低电压穿越技术研究

发布时间：2019-05-19 11:39

【摘要】：随着风电机组容量的增加,低电压穿越能力已经成为大型风电场并网准则的基本要求之一。风电场的低电压穿越能力既可以保护风力发电机组自身在故障下的安全,也可以提高电网的暂态稳定性,加速电网的故障恢复过程。双馈风机较小的变流器容量,限制了其低电压穿越能力的提高。这也使得双馈风机的低电压穿越技术成为目前研究的一大难点。对于双馈风机,抑制转子侧绕组的过电流是低电压穿越控制策略的主要目标。通常的控制方法是通过加快定子磁链的衰减速度,从而间接地抑制转子侧过电流。本文对双馈风力发电系统的结构和原理进行了研究,建立了双馈感应发电机的暂态数学模型,对双馈风机在电网电压跌落时的暂态特性进行了分析,研究了转子侧绕组出现过电流现象的机理。考虑到双馈风机定子和转子之间的强耦合性,推导了暂态电流模型,用以详细描述定子和转子电流的动态响应特性。然后基于建立的暂态电流模型,考虑同时对双馈风机定子和转子电流进行抑制,提出了直接电流幅值的低电压穿越控制策略。提出的控制策略可以很容易的实现动态的无功支持。为了穿越不对称故障,扩展了暂态电流模型的负序分量形式,并设计了同时抑制转子侧正负序电流的控制系统。为了验证提出方法的有效性,通过PSCAD仿真平台建立了 0.9 MW的双馈风机仿真系统。仿真结果表明提出的低电压穿越控制策略可以有效增强双馈风机穿越对称和不对称故障的能力。
[Abstract]:With the increase of wind turbine capacity, low voltage traversing capacity has become one of the basic requirements of grid-connected criteria for large wind farms. The low voltage traversing capacity of wind farm can not only protect the safety of wind turbine under fault, but also improve the transient stability of power grid and accelerate the fault recovery process of power grid. The small converter capacity of doubly-fed fan limits the improvement of its low voltage traversing capacity. This also makes the low voltage crossing technology of doubly fed fan become a big difficulty in the current research. For doubly-fed fan, suppressing the overcurrent of rotor side winding is the main goal of low voltage traversing control strategy. The usual control method is to indirectly suppress the rotor side overcurrent by speeding up the attenuation speed of the stator flux. In this paper, the structure and principle of doubly-fed wind power generation system are studied, the transient mathematical model of doubly-fed induction generator is established, and the transient characteristics of doubly-fed fan during voltage drop are analyzed. The mechanism of overcurrent phenomenon in rotor side windings is studied. Considering the strong coupling between stator and rotor of doubly-fed fan, the transient current model is derived to describe the dynamic response characteristics of stator and rotor current in detail. Then, based on the transient current model, considering the simultaneous suppression of stator and rotor current of doubly-fed fan, a low voltage traversing control strategy with direct current amplitude is proposed. The proposed control strategy can easily realize dynamic reactive power support. In order to cross the asymmetric fault, the negative sequence component of the transient current model is extended, and a control system is designed to suppress the positive and negative sequence current on the rotor side at the same time. In order to verify the effectiveness of the proposed method, a 0.9MW doubly-fed fan simulation system is established by PSCAD simulation platform. The simulation results show that the proposed low voltage traversing control strategy can effectively enhance the ability of doubly fed fan to pass through symmetrical and asymmetric faults.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM614

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